I just read in the 2008 "Book of the AR-15" that, due to high ammo costs, S&W plans to release a new M&P-15 model in 5.45x39 Russian. They said that the Russian ammo is an average of $200 cheaper per 1,000 rounds than 5.56mm and they wanted to produce a rifle that the "average" AR owner could actually afford to go out and shoot. I'm thinking that's all well and good, but I wonder how well the Russian round will feed in a magazine designed to fit an AR lower. Would'nt the 5.45x39 have some of the same feeding issues as the 7.62x39? They are both heavily tapered cases. Thoughts anyone?